Original Medicare, the federal health insurance program for seniors, does not cover prescription drugs. If you want coverage, you can buy a Medicare prescription drug (Medicare Part D) plan through a private insurer. Medicare Advantage policyholders typically have prescription drug benefits.

Medicare Part D and Medicare Advantage plans most likely will not cover all your prescription drug costs. Here’s how you can save money:

Shop around – Compare your policy premiums to those of other companies.

Check the formulary – Prescription plans have formularies, or lists of drugs they cover and the various tiers of coverage. Check the formulary for any drugs you regularly take.

Check the tier – Insurers separate their formularies into tiers by cost and other factors, such as proven effectiveness.

Opt for copayments if possible – Your plan probably requires either copayments or coinsurance. Copayments are flat fees you pay whenever you buy a prescription drug. Insurers charge lower copayments for generic and proven drugs to steer consumers towards those drugs vs. brand-name or experimental drugs. Coinsurance requires you to pay a percentage of the total prescription cost, which can be quite high depending on the drug.

Use generics when possible – Generic drugs cost much less than their brand-name counterparts, which can often save you 80 percent or more.

When to Sign Up

You are eligible to sign up for Part C or D (Medicare Advantage or Medicare Part D) coverage during a seven-month window, which starts three months before you turn 65 and ends four months after your birthday.

If you fail to enroll during this period, you could end up paying a late fee, which is permanently be added to your premiums if you go 63 or more days without prescription drug coverage after becoming eligible. You premium could be increased about one percent for every month you go without creditable drug coverage.

If you’re 65 years old or older and already enrolled in Medicare Part D, it is too late to switch coverage for 2017. You must wait for the next open enrollment Oct. 15 to Dec. 7, 2017.